In recent years, there is a rapid growth of carbon fiber-reinforced composites due to their low density, good strength, and possibility of combining the toughness of thermoplastic polymers with the stiffness and strength of the reinforcing carbon fibers. The epoxy resins as reinforced with carbon fibers have good mechanical properties and have been widely used for producing structural parts of aircraft and many other engineering products.
However, the carbon fiber reinforced epoxy resins have the defects “cavities” existing in the carbon fiber reinforced composites. Such cavities may be caused by the trapping of air pockets in the resin during the production step such as mixing, etc., or during the impregnation of the carbon fiber reinforcement. Macro porosities are majorly present during low viscosity impregnation of the carbon fiber reinforcement while micro pores are caused when the impregnation are conducted in high-viscosity capillary flow. Such porosities or pores may cause a poor interfacial adhesion between the carbon fiber and the epoxy resin, which may then result in “debonding” of carbon fibers from the matrix epoxy resin, thereby making the composite product of carbon fiber reinforced epoxy resin easily brittle or fractured.